A light-receiving device incorporated in a light-receiving module for remote control applications is generally composed of a light-receiving device for infrared light. Conventionally known examples of such light-receiving devices are those having a light-receiving portion composed of a PIN-type diode formed in the thickness direction of a substrate as shown in FIG. 9 or along the surface of a substrate as shown in FIG. 10. In FIG. 9, reference numeral 101 represents a P− layer, reference numeral 102 represents a P+ layer, reference numeral 103 represents an N+ layer, reference numeral 104 represents an insulating layer of SiO2, reference numeral 105 represents an N electrode, and reference numeral 106 represents a P electrode. The structure shown in FIG. 9 has the disadvantage that carriers 107 ascribable to long-wavelength light components that have reached the P+ layer 102 diffuse (indicated by arrow Lp) and produce a photoelectric current. On the other hand, in FIG. 10, reference numeral 201 represents a depletion layer (of which the thickness is represented by W), reference numeral 202 represents a P+ layer, reference numeral 203 represents an N+ layer formed in the shape of a ring, reference numeral 204 represents an insulating layer of SiO2, reference numeral 205 represents a P electrode, and reference numeral 206 represents an N electrode. The structure shown in FIG. 10 has the disadvantage that even carriers 207 ascribable to long-wavelength light components which appear outside the depletion layer 201 produce a photoelectric current within the diffusion length (Lp) of the carriers 207. In this way, in conventional light-receiving devices, reception of light having longer wavelengths than the desired wavelengths may cause a malfunction.
Light-receiving devices like this are usually used in a form covered with a visible light shielding resin to prevent malfunctions due to visible light. Moreover, such light-receiving devices are extremely susceptible to electromagnetic noise, and this also leads to malfunctions in light-receiving modules incorporating them. To prevent this, a conductive film (metallized film) or the like is inserted in a light-receiving module, or a mesh-like structure is arranged in the light-receiving window of a module case. On the other hand, in a light-receiving module sealed with a resin instead of being furnished with a metal case, a mesh-like metal conductive member is formed on the surface of a light-receiving device incorporated therein.
In illumination apparatus employing an infrared light-receiving module, the effects of visible light are coped with by the use of a light-receiving module or light-receiving device covered with a visible light shielding resin. In reality, however, illumination apparatus are fitted with a band-path filter or the like to alleviate the effects of light from a fluorescent lamp which contains light components at many wavelengths spread across its spectrum. Moreover, in recent years, as it becomes increasingly common to use a plurality of fluorescent lamps together or to use fluorescent lamps with increasingly high outputs, more attention than ever has come to be paid to malfunctions of light-receiving modules ascribable to light components at particular wavelengths (for example, at 1,013 nm) within the spectrum of the light from a fluorescent lamp. For these reasons, light-receiving modules in practical use either have an interference filter arranged on top of a light-receiving device covered with a visible light shielding resin so as to receive signals cleared of unwanted light components having particular wavelengths within the spectrum of the light present, or have an interference filter embedded in a visible light shielding resin.
This increases the number of components and the number of assembly steps required to fabricate light-receiving modules, and thus increases their costs. Moreover, in a case where an interference filter is embedded in a resin, it is difficult to achieve satisfactory reliability in terms of the accuracy with which the interference filter is fitted, exfoliation of the resin from the interference filter, and other factors.
Moreover, in a light-receiving module sealed in a resin, a mesh-like metal conductive member is formed on an internal light-receiving surface, and forming such a conductive member directly on the surface of a light-receiving device is equivalent to forming a parallel-plate capacitor there. This increases the capacitance of the device, and thus shortens the distance over which the light-receiving module incorporating it can receive signals.